Electronic timepiece with solar cell

ABSTRACT

In the present invention, a light permeable dial trim ring is arranged on the inner side of a solar cell, and a part of a solar cell photovoltaic area and a part of the dial trim ring which covers the solar cell photovoltaic area are arranged to be lower than a dial upper surface height. Further, a dial thickness of the dial inner side is set larger than a thickness of a dial peripheral edge on which the light permeable dial trim ring is mounted while assuring a light leading portion for a light which enters the dial trim ring. Alternatively, a flange portion which fixes a glass to a watch case is arranged outside the light permeable dial trim ring and the solar cell, the dial trim ring is arranged directly below the glass, and a blind portion is provided above the dial trim ring or the solar cell. As a result, a gap between the glass lower surface and the dial upper surface can be reduced, thereby eliminating a “hollow-eyed” design.

TECHNICAL FIELD

The present invention relates to an electronic watch with a solar cellwhich is arranged in a dial trim portion in a watch having a solar powergeneration system which generates a power by utilizing a light and acharging system which charges a power generated by this solar powergeneration system.

BACKGROUND ART

Many electronic watches each of which has a solar cell and utilizes alight such as a sunlight as a power generation source have beenconventionally commercialized. In these electronic watches, a dial isrestricted in design when a solar cell is arranged under the lightsemi-permeable dial, and hence commercial products having variousdesigns cannot be proposed.

That is, since a surface of the solar cell has a dark brown color, thedial must be mounted on the solar cell in order to hide the color ofthis surface. On the other hand, in order to generate a power uponreceiving a light by the solar cell, the dial must have properties whichtransmit a light therethrough to some extent, i.e., the lightpermeability. Therefore, even if an attempt to change a color of thedial to white is made, the dial has a grayish color tone like frostedglass, a beautiful white color cannot be provided, and hence there is arestriction in design.

Meanwhile, a reduction in power consumption of watches has advanced inrecent years, and watches can be driven even if a superficial content ofa solar cell is reduced to some extent. Thus, there has been proposed anelectronic watch with a solar cell which is arranged on an outerperiphery of a dial substantially vertically to the dial. As such aconventional example, there is a watch in which a solar cell formed on aflexible strip-like printed board is wound on a wall surface of a gapportion between a glass and a dial, which is disclosed in JapaneseUtility Model Application Laid-open No. 42390-1987 (Patent Reference 1)or Japanese Patent Application Laid-open No. 2002-148366 (PatentReference 2).

FIG. 10 is a cross-sectional view of a watch according to a firstembodiment illustrated in FIG. 1 of Patent Reference 1. This watch has asolar cell block 23 in which a plurality of solar cells 20 are bonded toa printed board 21 and accommodated in a groove portion 22 a of asupport ring 22. This solar cell block 23 is arranged below a flangeportion 26 which fixes a glass 24. A pent roof portion 22 d whichconnects an inner peripheral ring 22 b with an outer peripheral ring 22c is formed to the support ring 22. Further, the solar cells 20 have aconfiguration in which the solar cells 20 are arranged on a dial 25.

FIG. 11 is a cross-sectional view of a watch according to a secondembodiment illustrated in FIG. 3 of Patent Reference 1. In this watch, asolar cell unit 36 is arranged in a gap portion between a glass 33 and adial 34 in a state where the solar cell unit 36 is wound on an innerside of an inner wall surface of a dial trim portion 31 of a watch case35. This solar cell unit 36 is formed by bonding a solar cell 30 madeout of amorphous silicon is bonded to a stainless sheet 32.

Further, FIG. 12 is a cross-sectional view of a watch according to afirst embodiment of Patent Reference 2. In this watch, a ring-shapedbank 45 is provided above a position at which a dial 43 of a watchmovement 44 is arranged, and a solar cell 40 is arranged on an innerwall surface 46 of this bank 45. It is to be noted that referencenumeral 41 denotes a glass and reference numeral 42 designate a flangeportion on the side.

In the structure shown in FIG. 10, however, a gap dimension between theglass 24 and the dial 25 is a dimension obtained by adding up heights ofthe flange portion 26, the pent roof portion 22 d and others as well asthe solar cell 20. Therefore, the gap between the glass 24 and the dial25 becomes large, resulting in a design problem that a position of thedial 25 is deeply set as seen from the glass 24, which is a so-called“hollow-eyed watch”. Furthermore, a hand position is deeply set or ahand gap is wide, and the design properties are deteriorated, therebylowering a commercial value.

Moreover, in the structure shown in FIG. 11, the gap between the glass33 an the dial 34 is narrowed since the flange portion is eliminated,but a width of the cell must be increased to some extent because ofperformances of the current solar cell, a height of the cell is large,and a gap of the cell is still wide. Additionally, since the solar cell30 is exposed in the gap portion between the glass 33 and the dial 34,there occurs a design problem that the dark brown color inherent to thesolar cell can be directly seen from the outside of the watch 35 and thesolar cell 30 is distinctive as a black ring in case of a dial having abright color in particular.

In the structure shown in FIG. 12, like the conventional exampledepicted in FIG. 10, the solar cell 40 is arranged below the flangeportion 42 which fixes the glass 41. Therefore, the gap between theglass 41 and the dial 43 has a dimension obtained by adding up not onlya height of the solar cell 40 but also a height of the flange portion,and hence the gap between the glass 41 and the dial 43 becomes wide. Asa result, there occurs a design problem that a position of the dial 43is deeply set as seen from the glass 41, thereby leading to a so called“hollow-eyed watch”.

As described above, in the prior art, the solar cell must have a fixedsuperficial content in order to obtain an energy which is sufficient todrive the watch and, even in case of a men's watch having a large dialtrim diameter, i.e., a watch which can have an increased length of thesolar cell, if the watch has a black dial, a necessary height of thesolar cell becomes larger than a height of the gap between the glass andthe dial in a watch which is not based on the solar power generation. Asa result, there occurs a problem that the “hollow-eyed watch” isobtained.

Therefore, it is an object of the present invention to provide a watchwhich can assure a power generation quantity required to drive thewatch, make a solar cell indistinctive but does not give a sense of thedepth of a dial position in an electronic watch with a solar cell whichis arranged substantially vertically with respect to a dial.

DISCLOSURE OF THE INVENTION

The present invention has, in an electronic watch with a solar cellwhich is arranged substantially vertically with respect to a dial, astructure in which a light leading portion is provided at a peripheraledge of the dial, a light permeable dial trim ring is arranged at theperipheral edge of the dial and a part of the solar cell powergeneration area and a part of the dial trim ring which covers the powergeneration area of the solar cell are arranged to be lower than an uppersurface height of the dial.

Although the light permeable dial trim ring and the dial are arranged inthe solar cell, a light which is used to generate a power required fordriving the watch can be taken in by providing the light leading portionwhich is an inlet for the light. Further, an incident light from thedial trim ring can be led to the solar cell arranged below the dialupper surface by arranging a part of the solar cell power generationarea and a part of the dial trim ring which covers the solar cell powergeneration area to be lower than the upper surface height of the dial.As a result, it is not necessary to arrange the entire solar cell to behigher than the upper surface of the dial, a gap between a glass lowersurface, and the dial upper surface can be reduced to be equivalent tothe gap of a conventional electronic watch having a primary battery,thereby eliminating the problem of the “hollow-eyed watch”.

Furthermore, the present invention has a configuration in which athickness of the inner side of the dial is larger than that of theperipheral edge.

By setting a thickness of the inner side of the dial where watch handsare arranged to be larger than a thickness of the peripheral edge of thedial where the dial trim ring is arranged, a gap from the glass lowersurface to the dial upper surface can be narrowed while assuring asuperficial content of a light incidence surface with respect to thedial trim ring required to generate a power which is necessary fordriving the watch, thereby eliminating the “hollow eye” problem.

Moreover, the present invention has a structure in which the lightleading portion has an inclined surface portion configured in such amanner that the thickness of the dial is reduced from the inner sidetoward the peripheral edge side.

Although a difference in thickness of the dial is produced by increasingthe thickness of the inner side of the dial to be larger than thethickness of the peripheral edge, this difference can be madeindistinctive by providing the inclined surface.

Additionally, in the present invention, the light leading portion isconfigured in such a manner that the thickness of the dial becomes smallat the peripheral edge.

Although a step can be readily formed to the outer peripheral portion ofthe dial by press working, milling or the like, formation of the stepcan be likewise realized by attaching two circular plates havingdifferent outside diameters to each other, and there is a merit that theprocessing is easy as compared with a configuration in which an inclinedsurface is formed.

Further, the present invention has a structure in which an inclinedsurface portion is provided to the dial trim ring and an inclinedsurface or a step portion of the light leading portion of the dial iscovered with the inclined surface portion.

By arranging the dial trim ring which covers the inclined surface or thestep portion which is generated due to a difference in thickness betweenthe inner side and the peripheral edge of the dial, the light leadingportion which takes in a light with which a power generation quantityrequired to drive the watch can be assured is provided, and it ispossible to realize an external appearance which has a flat dial as anexternal appearance of the watch and which is not different from aconventional electronic watch having a primary battery.

The present invention has a structure in which a flange portion whichfixes a glass to a watch case is provided outside the dial trim ring,the solar cell and a watch movement or an annular convex portion of acasing frame which holds the solar cell, the dial trim ring is arrangeddirectly below the glass, and a blind portion is provided above the dialtrim ring of the glass and/or the solar cell in the watch case of theelectronic watch with a solar cell.

Since the dial trim ring can be arranged directly below the glass, thegap between the glass and the upper surface of the dial can be reducedfor an amount corresponding to the thickness of the flange portion, thegap equivalent to that of a conventional electronic watch having aprimary battery can be obtained, and the solar cell can be hidden from aposition directly above the glass.

As a result, the gap between the lower surface of the glass and theupper surface of the dial can be reduced by increasing the thickness ofthe inner side of the dial to be larger than the thickness of theperipheral edge of the dial while assuring the light leading portion fora light which enters the dial trim ring, thereby eliminating the“hollow-eyed” design.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a primary part of an electronicwatch with a solar cell, showing Embodiment 1 of a first embodimentaccording to the present invention;

FIG. 2 is a cross-sectional view of a primary part of an electronicwatch with a solar cell, showing a second embodiment according to thepresent invention;

FIG. 3 is a plan view of a solar cell according to the presentinvention;

FIG. 4 is a perspective view showing a state of the solar cell assembledin the watch according to the present invention;

FIG. 5 is a plan view of a movement of the electronic watch with thesolar cell according to the present invention;

FIG. 6 is a graph showing a light receiving efficiency with respect to adial thickness based on Embodiment 1 of the first embodiment accordingto the present invention;

FIG. 7 is a cross-sectional view of a primary part of an electronicwatch with a solar cell, showing a conformation with a different dialtrim ring based on Embodiment 2 of the first embodiment according to thepresent invention;

FIG. 8 is a cross-sectional view of a primary part of an electronicwatch with a solar cell, showing a conformation with a different dialshape based on Embodiment 3 of the first embodiment according to thepresent invention;

FIG. 9 is a cross-sectional view of a primary part of an electronicwatch with a solar cell in which a solar cell is arranged in a casingframe, which is another conformation of Embodiment 1 of the firstembodiment according to the present invention;

FIG. 10 is a cross-sectional view of a primary part of an electronicwatch with a solar cell according to a prior art described in PatentReference 1;

FIG. 11 is a cross-sectional view of a primary part of an electronicwatch with a solar cell according to the prior art described in PatentReference 1; and

FIG. 12 is a cross-sectional view of a primary part of an electronicwatch with a solar cell according to a prior art described in PatentReference 2.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments according to the present invention will now be describedhereinafter with reference to the accompanying drawings.

It is to be noted that the present invention is not restricted theembodiments.

First Embodiment

FIG. 1 is a cross-sectional view of a primary part of an electronicwatch with a solar cell showing a first embodiment according to thepresent invention, FIG. 3 is a plan view of a solar cell of theembodiment according to the present invention, and FIG. 4 is aperspective view showing a state of the solar cell assembled in thewatch of the embodiment according to the present invention.

First, a structure of the solar cell will be described with reference toFIG. 3. The solar cell 1 is obtained by forming an amorphous siliconlayer or the like on a PET film of a base substrate, and it is aflexible solar cell having a thickness of approximately 150 μm and anelongated strip-like shape by which the solar cell can be bent andaccommodated in a watch case as shown in FIG. 4.

The solar cell 1 according to this embodiment is an electric cell, andreference numeral 1 a denotes a photovoltaic area; 1 b and 1 c, positiveand negative electrodes which are used to take out a generated power;and 1 d, a protrusion having a positioning hole which is used whenassembling the solar cell in a watch movement. Further, an edge portion1 e having a width of approximately 400 μm where no power is generatedeven if a light is applied thereto is provided on the entire outerperiphery of the photovoltaic area 1 a, this is a cutting width which isused when cutting and separating each solar cell from a sheet obtainedby forming many solar cells on a PET film. At the time of assembling,the solar cell is assembled into the watch in an annular form in such amanner that the photovoltaic area 1 a faces the center of the watch asshown in FIG. 4.

In this embodiment, a circuit support 3 is extended in the verticaldirection, and a part extended to the upper side is further extended toa glass 4 side, thereby forming an annular convex portion 3 a. The solarcell 1 has the flexibility as described above, it is curled up andincorporated on an inner wall surface 3 b of the annular concave portion3 a of the circuit support 3, and it is attached in such a shape asshown in FIG. 4 on the inner wall surface 3 b of the convex portion 3 aby the tensile force of the stretching solar cell itself.

A dial 5 is mounted oh the circuit support 3 provided on the watchcenter side apart from the solar cell 1 arranged in the annular form. Alight permeable dial trim ring 2 is arranged on a peripheral edge 5 a ofthis dial 5. That is, there is adopted a structure in which the dialtrim ring 2 is arranged on the inner side of the solar cell 1. The dial5 does not have an even thickness, and a thickness of the dial innerside 5 b on which hour, minute and second hands 11 are arranged islarger in the glass 4 direction than a thickness of a dial peripheraledge 5 a on which the dial trim ring 2 is mounted. Further, an inclinedsurface portion 5 d which is configured so that the thickness of thedial is reduced toward the peripheral edge side 5 a from the inner side5 b is formed at a position filling a difference between the dialperipheral edge 5 a and the dial inner side 5 b.

This difference and the inclined surface 5 d form a light leadingportion 2 a for a light, thereby assuring a fixed width of an inlet of alight with respect to the dial trim ring 2. As a result, a necessarypower generation quantity can be assured and, at the same time, a gapbetween the glass 4 and the dial 5 can realize a depth comparable tothat of a conventional electronic watch having a primary battery byincreasing the dial thickness of the dial inner side 5 b.

Furthermore, a part of the photovoltaic area 1 a (a hatched part of thesolar cell 1 in FIG. 1) of the solar cell 1 and a part 2 b of the dialtrim ring 2 which covers the photovoltaic area 1 a of the solar cell 1are arranged below a position of a dial upper surface 5 c. By doing so,a gap from the glass 4 to an upper surface of the dial peripheral edge 5a on which the dial trim ring 2 is arranged can be narrowed. Moreover, alight transmitted through the dial trim ring 2 which is a light leadingmember is emitted from the part 2 b of the dial trim ring 2, and a powercan be likewise generated in the part of the solar cell 1 arranged belowthe position of the dial upper surface 5 c.

Additionally, an air layer 9 exists between the dial trim ring 2 and thesolar cell 1, and a part of the light transmitted through the dial trimring 2 is reflected and scattered on an interface, thereby making ithard to see the dark brown color of the solar cell 1 from the outside.

Further, the electrode portions 1 b and 1 c of the solar cell 1 protrudeto a case back 10 side via a hole portion 6 a of the watch movement 6.Two connection springs 8 are arranged on the case back 10 side. Thisconnection spring 8 is fixed to a non-illustrated circuit board througha plate holding an insulating sheet. An end portion 8 a of thisconnection spring 8 is brought into contact with the positive andnegative electrodes 1 b and 1 c of the solar cell so that the generatedpower from the solar cell 1 is led to the circuit board.

FIG. 5 is a plan view showing the watch movement 6 depicted in FIG. 1from the case back side, and shows an arrangement relationship of thetwo connection springs 8, the solar cell 1 and others in plan. Theconnection spring 8 is held and fixed by a screw 8 b or the like inorder to achieve electrical connection between the solar cell 1 and thecircuit board.

Embodiment 1

A description will now be given as to a difference in power generationperformance between an electronic watch with a solar cell using the dial5 having a large thickness on the inner side 5 b and an electronic watchwith a solar cell using a flat dial with reference to Table 1, FIG. 1and FIG. 6.

In case of a general flat dial, a thickness A is approximately 400 μm.On the contrary, as to the dial shown in FIG. 1, the power generationperformance was measured when a dimension D of the peripheral edge 5 aon which the dial trim ring 2 is mounted is determined as 300 μm and athickness B of the inner side 5 b which is increased by providing theinclined surface at an angle of 45 degrees from the inner periphery ischanged to 700 μm and 1000 μm, and Table 1 shows a result of thismeasurement. It is to be noted that a lower end of the photovoltaic area1 a of the solar cell at this moment is placed at a position reachingthe same height as the lower surface 5 e of the dial 5. TABLE 1 PowerLight Dial generation receiving Gap dimension thickness (B) current lopefficiency from glass to (μm) (μA) (%) *1 dial (C) (μm) 400 (=A) 12.721.1 2150  700 11.9 19.9 1850 1000 11.3 18.9 1550A state when assembled in a finished watchThe Illuminance = 500 lux; an operating voltage = 0.45 VA color of the dial = blackn = an average value of 5*1 a percentage of an acquired current with respect to a powergeneration current 60 μA of a horizontally set solar cell.

Table 1 shows measured values of the power generation current and thelight receiving efficiency in a finished watch when the dial thickness Bis changed and the gap dimension C from the glass to the dial under thecondition that the illuminance is 500 lux, a solar cell operatingvoltage is 0.45 V and a color of the dial is black.

It is to be noted that the light receiving efficiency is a percentage ofa power generation current when a light having the same illuminance asthat of the single solar cell unit is applied from a directionorthogonal to the dial (a direction parallel to the solar cell) in thefinished watch in which the solar cell is assembled with respect to apower generation current value when a light is applied from a directionvertical to the photovoltaic area in a state where the single solar cellunit is horizontally placed, and a measured value indicates an averagevalue of n=5. Moreover, the dial trim ring used in the measurement isformed of transparent and colorless polycarbonate resin which has thelight permeability by injection molding, and a surface of the dial trimring is a glossy surface.

As shown in Table 1, the light receiving efficiency is 21.1% in the dialwith an even thickness whose dial thickness is 400 μm, whereas the lightreceiving efficiencies are 19.9% and 18.9% in the dial whose dialthickness is set to 700 μm and 1000 μm by increasing the thickness ofthe dial inner side.

FIG. 6 shows the data of Table 1 in the form of a graph of the lightreceiving efficiency with respect to the dial thickness, and there isindicated a tendency that the light receiving efficiency is lowered asthe dial thickness is increased as shown in FIG. 6. This result impliesthat the light leading portion 2 a for a light is narrowed as thethickness (B) of the dial 5 depicted in FIG. 1 is increased and a lightis hence hard to enter, and this is a natural consequence.

A relationship between a watch power consumption and a power generationquantity by the solar cell will now be described.

[About Watch Power Consumption]

A specification of an electronic watch with a solar cell used in thedescription of this embodiment is an analog watch with three hands and adate, and it is determined that a watch power consumption=0.53 μA.Therefore, there is obtained a power consumption required for drivingthe hands fora day=a watch power consumption×24 hr=12.7 μA·Hr  (1)[About Power Generation Quantity]

A specification of the solar cell utilized by the watch used in thisembodiment is as follows:Solar cell outside size=a length 92.1 mm, a width 2.4 mm Solar celllight receiving portion effective size=a length 91.3 mm, a width 1.6 mmA  power  generation  effective  superficial  content = 146  mm²  (a  peripheral  edge  width = approximately  0.4  mm)

The number of solar stages=one

In regard to the power generation performance of the solar cell, theilluminance is 500 lux, an operation voltage is 0.45 V, and a powergeneration current when the solar cell is horizontally set=60 μA.

In regard to the electronic watch with the solar cell according to thisembodiment, an open circuit voltage Voc of the solar cell in theelectronic watch using one stage of the solar cell is 0.6 V, and thepower generation voltage must be boosted in order to charge an Lisecondary battery with a rated voltage of 1.35 V. As to a specificationof a booster system, assuming that a boosting ratio is threefold and aboosting efficiency is 90%, a power generation quantity in the finishedwatch under the average light irradiation condition per day can becalculated based on the following expression:=an irradiation time×a power generation current×a light receivingefficiency+a boosting ratio×a boosting efficiency  (2)

Incidentally, it is assumed that the average light illuminance per dayis 500 lux and the average irradiation time is 4 hr.

If the power generation quantity in the finished watch under the averageirradiation condition per day in (2) is larger than the powerconsumption required for driving hands for a day in (1), the finishedwatch can be realized as a watch, and the minimum light receivingefficiency for this realization can be calculated based on the followingexpression. That is,A watch power consumption×24 hr≦an irradiation time×a power generationcurrent×a light receiving efficiency+a boosting ratio×a boostingefficiency.

Therefore,the  minimum  light  receiving  efficiency = a  watch  power  consumption × 24  hr ÷ an  irradiation  time ÷ a  power  generation  current × a  boosting  ratio ÷ a  boosting  efficiency = 0.53  μ  A × 24  hr ÷ 4  hr ÷ 60  μ  A × 3 ÷ 90% = 17.7%

Accordingly, if the light receiving efficiency is not less than 17.7%,the finished watch can be realized as a watch.

The gap dimension C between the glass and the dial of the conventionalelectronic watch with three hands having a primary battery isapproximately 1500 to 1600 μm, whereas, when the dial thickness B is1000 μm as shown in Table 1, the gap dimension C is 1550 μm which isequivalent to that of the conventional electronic watch with three handshaving the primary battery, and the light receiving efficiency at thistime is 18.9%. Therefore, a value larger than the calculated value 17.7%of the minimum light receiving efficiency can be obtained, the powergeneration quantity with which the watch can function can be obtained,and the gap dimension between the glass and the dial can be setequivalent to that of the conventional watch with three hands having theprimary battery.

Embodiment 2

FIG. 7 is a cross-sectional view of a primary part of an electronicwatch with a solar cell according to the present invention, showingEmbodiment 2. In Embodiment 2, as compared with FIG. 1, the inclinedsurface portion 2 c in the light leading portion 2 a of the dial trimring 2 is caused to project toward the central side of the watch, anextension line of the inclined surface of the inclined surface portion 2c is set to cross an extension line of the wall thickness upper surface5 c of a wall thickness portion (B) of the dial 5, and 5 d as theinclined surface of the light leading portion of the dial 5 is coveredwith the inclined surface 2 c. When the dial trim ring 2 is formed intoa shape with which the dial inclined surface 5 d is covered as shown inFIG. 7, the step between the dial trim ring 2 and the dial inclinedsurface portion 5 d shown in FIG. 1 can be eliminated, and a superficialcontent of the light leading portion 2 a for a light with respect to thesolar cell 1 can be assured.

Embodiment 3

FIG. 8 is a cross-sectional view of a primary part of an electronicwatch with a solar cell according to the present invention, showingEmbodiment 3. In Embodiment 3, as compared with FIG. 1, the inclinedsurface portion 2 c in the light leading portion 2 a of the dial trimring 2 is caused to project toward the central side of the watch, anextension line of the inclined surface of the inclined surface portion 2c is set to cross an extension line of the wall thickness upper surface5 c of the wall thickness portion (B) of the dial 5, and 5 d as theinclined surface of the light leading portion of the dial 5 is coveredwith the inclined surface portion 2 c. When a superficial content of thelight leading portion 2 a for a light with respect to the solar cell 1is assured as shown in FIG. 8, it is possible to adopt a structure inwhich the dial peripheral edge 5 a and the dial inner side 5 b of thedial 5 are connected with each other through the step. Althoughformation of the step at the dial outer peripheral portion can bereadily performed by press working, milling or the like, this formationcan be likewise realized by attaching two circular plates havingdifferent outside diameters to each other, and there is a merit thatprocessing is facilitated as compared with the structure in which aninclined surface is formed.

Embodiment 4

FIG. 9 is a cross-sectional view of a primary part of an electronicwatch with a solar cell according to the present invention, showingEmbodiment 4 of the present invention. In Embodiment 1 to Embodiment 3,the description has been given on the structure in which the solar cell1 is arranged at the annular convex portion 3 a which is provided to thecircuit support 3 as a component of the watch movement 6 and used forpositioning the solar cell 1. FIG. 9 shows a structure in which anannular convex portion 50 a which is used for positioning of the solarcell is provided in a casing frame 50 as an exterior component which isused when accommodating the watch movement 6 in the watch case 12 andthe solar cell 1 is arranged on an inner wall surface 50 b of thisconvex portion 50 a. Embodiment 4 can be carried out in the watchstructure in Embodiment 2.

It is to be noted that the casing frame is an exterior component whichaccommodates and holds the watch movement in the watch case whenassembling the watch movement in the watch case, and also absorbs impactshocks from the outside of the watch.

Embodiment 5

In FIG. 7, a reflection film comprising a thin film of, e.g., aluminumis attached on a surface 2 d (a surface indicated by a broken line)which is not a surface which emits a light toward the solar cell byvapor deposition or the like on a light incidence surface of the dialtrim ring 2 which takes in an external light. The reflection film canprevent a light from leaking toward the outside of the dial trim ring 2from the surface 2 d, and a quantity of the light which enters the solarcell 1 can be thereby increased, thus increasing a power generationquantity.

Moreover, in FIGS. 1, 2, 8 and 9, a power generation quantity can belikewise increased by providing the reflection film to the dial trimring.

It is to be noted that the light receiving efficiency also variesdepending on a color of the dial, and the light receiving efficiency isincreased when the dial having a white color or a bright color whichreadily causes reflection of a light on the dial is used, whilst thelight receiving efficiency is reduced when a color of the dial is black.In regard to the black color and the white color as the dial color, thelight receiving efficiency is doubled or more when the white color isused.

As described above, according to the first embodiment, in the electronicwatch with the solar cell which is arranged substantially verticallywith respect to the dial, the gap between the glass lower surface andthe dial upper surface can be reduced by arranging the light permeabledial trim ring on the inner side of the solar cell and also arranging apart of the solar cell photovoltaic area and a part of the dial trimring which covers the solar cell photovoltaic area to be lower than thedial upper surface height, and by increasing the dial thickness of thedial inner side to be larger than the thickness of the dial peripheraledge on which the dial trim ring is mounted while assuring a quantity ofa light which enters the solar cell which is used to obtain a powerrequired for driving the watch, and this gap is set equivalent to thatof the conventional electronic watch having a primary battery, therebyeliminating the hollow-eyed appearance.

Second Embodiment

FIG. 2 is a cross-sectional view of a primary part showing a secondembodiment of the present invention. In this embodiment, the watchmovement 6 described in the first embodiment in which the lightpermeable dial trim ring 2 is attached on the outer periphery of thedial 5 is used, but a general flat dial 5 having a thickness of 400 μmis used as the dial 5. Additionally, the flange portion 13 which holdsand fixes the glass 4 is incorporated in the watch case 12 which ispositioned on the outer side and the upper surface side of the solarcell 1 and the dial trim ring 2. The solar cell 1 and the dial trim ring2 are arranged directly below the glass 4 in close proximity, and anannular print 4 a or the like is provided on the lower surface of theglass 4 at a position where the solar cell 1 and the dial trim ring 2are arranged.

A thickness of the flange portion 26 in the prior art shown in FIG. 10can be eliminated by placing the flange portion 13 which accepts andfixes the glass 4 in the watch structure shown in FIG. 2 on the outerside of the solar cell 1 and the dial trim ring 2. As a result, the gapbetween the glass 4 and the dial 5 is 2150 μm when the dial 5 having athickness of 400 μm is used as described in connection with Embodiment1, whereas this gap can be reduced to 1700 μm. This gap becomessubstantially equivalent to that of the conventional electronic watchwith three hands having a primary battery, and the “hollow-eyed” designcan be eliminated.

Further, the solar cell 1, the dial trim ring 2 and others can becovered so that they are invisible from the outside of the watch case 12by providing the annular print or a metallic film 4 a to the glass lowersurface directly above the dial trim ring 2 and the solar cell 1,thereby improving the external appearance quality.

In regard to a power generation quantity of the watch described in thesecond embodiment, the light receiving efficiency is approximately 21.1%which is equivalent to that obtained when a flat dial having a dialthickness of 400 μm is used in the first embodiment, and the sufficientpower generation quantity is obtained as compared with the watch havingthe specification described in Embodiment 1 of the first embodiment.

It is to be noted that the description has been given by using the solarcell which is a strip-like electronic cell in this embodiment, it ispossible to use a solar cell such as a two-stage cell in which right andleft solar cells having the same size are provided.

As described above, according to the second embodiment, in theelectronic watch with the solar cell which is arranged substantiallyvertical with respect to the dial, the gap between the glass lowersurface and the dial upper surface can be narrowed by arranging thelight permeable dial trim ring on the inner side of the solar cell andplacing a part of the solar cell photovoltaic area and a part of thedial trim ring which covers the solar cell photovoltaic area to be lowerthan the dial upper surface height, and the “hollow-eyed” design can beeliminated by setting this gap to be equivalent to that of theconventional electronic watch having a primary battery.

INDUSTRIAL APPLICABILITY

According to the present invention, the gap between the glass lowersurface and the dial upper surface can be narrowed by increasing thethickness of the dial inner side to be larger than the thickness of thedial peripheral edge while assuring the light leading portion for alight which enters the dial trim ring, thereby providing the electronicwatch with the solar cell in which the “hollow-eyed” design iseliminated.

1. An electronic watch with a solar cell which is arranged substantially vertically with respect to a dial, wherein a light leading portion is provided at a peripheral edge of the dial, a light permeable dial trim ring is arranged at the peripheral edge of the dial, and a part of a photovoltaic area of the solar cell and a part of the dial trim ring which covers the photovoltaic area of the solar cell are arranged to be lower than a dial upper surface height.
 2. The electronic watch with a solar cell according to claim 1, wherein a thickness of the inner side of the dial is set larger than that of the peripheral edge.
 3. The electronic watch with a solar cell according to claim 1, wherein the light leading portion has an inclined surface portion which is configured in such a manner that a thickness of the dial is reduced from the inner side toward the peripheral edge side.
 4. The electronic watch with a solar cell according to claim 1, wherein the light leading portion has a step portion configured in such a manner that a thickness of the dial is reduced at the peripheral edge.
 5. The electronic watch with a solar cell according to claim 3, wherein an inclined surface portion is provided to the dial trim ring, and an inclined surface or a step portion of the light leading portion of the dial is covered with the inclined surface portion.
 6. The electronic watch with a solar cell according to claim 1, wherein a flange portion which fixes a glass to a watch case of the electronic watch with the solar cell is provided outside the dial trim ring, the solar cell and a watch movement or an annular convex portion of a casing frame which holds the solar cell; the dial trim ring is arranged directly below the glass; and a blind portion is provided above the dial trim ring of the glass and/or the solar cell. 